Is it possible for a DNS LoadBalancer RoundRobbin to do Graceful degradation?

Question

I need to setup a LoadBalancing DNS entry, so a classic round robbin mechanism, given the following diagram:

                         ________________
                        |                |
                        |     CLIENT     |
                        |  WEB BROWSER   |
                        |________________|
                                ||
                                ||
                         _______\/_______
                        |                |
                        |   DNS SERVER   |
                        |________________|
                                ||
                                ||
                        _______/  \_______
                       /                  \
                      /                    \
     ____________________                ____________________
    |                    |              |                    |
    |    Instance A      |              |      Instance B    |
    |____________________|              |____________________|
    |   ______________   |              |   ______________   | 
    |  |              |  |              |  |              |  |
    |  |   Service X  |  |              |  |   Service X  |  |
    |  |              |  |              |  |              |  |
    |  |              |  |              |  |              |  |
    |  |______________|  |              |  |______________|  |
    |____________________|              |____________________|

If instance B should fail, how to configure the DNS to ShortCircuit Instance B and Fallback 100% of the calls to Instance A.

Is this possible at the DNS level?

Thank you.

EN

Answer 1

If you have DNS requests running over TCP then may be you can otherwise most of the DNS queries run on UDP.

Some of the premimum DNS service providers might offer this as an service.